Add a function imx9_lpspi_select_cs to assert CS at the start of
an SPI transfer and keep it asserted until called again to
de-assert it. This can be called by board-provided imx9_lpspi_select,
in case the CS needs to be controlled via the LPSPI block and not
GPIO.
The TCR register CONT (continue) bit is asserted to prevent CS toggling
during the transfer, and the PCS bits are set to mark the correct CS
Signed-off-by: Jukka Laitinen <jukka.laitinen@tii.ae>
f641298d9e